I think that the ride with your wife depleted your stores just enough that you noitced the lack of real food before you got to work. On your "normal" rides you have just enough stored up to make the whole trip. I recommend eating a breakfast with some substance. French toast works well for me. Whole-grain cereal with milk and fruit also works, but I get fewer miles out of it.

Losing weight is more about the quality of what you eat than the quantity.